MLA
Ebbert, Isaa, Sutton, Jess, Soule, Joshua, 1781-186, Cope, Samuel W. Letter from Isaac Ebbert, Jesse Sutton, and Samuel W. Cope to Robert Paine - December 1, 1849. December 1, 1849. Robert Paine Papers, 1828-1882. Pitts Theology Library. https://digital.library.emory.edu/purl/767wm37r24-cor.
APA, 6th edition
Ebbert, Isaa, & Sutton, Jess, & Soule, Joshua, 1781-186, & Cope, Samuel W. (December 1, 1849)[Letter from Isaac Ebbert, Jesse Sutton, and Samuel W. Cope to Robert Paine - December 1, 1849]. Robert Paine Papers, 1828-1882, Pitts Theology Library. https://digital.library.emory.edu/purl/767wm37r24-cor.
Chicago
Ebbert, Isaa, Sutton, Jess, Soule, Joshua, 1781-186, Cope, Samuel W, Letter from Isaac Ebbert, Jesse Sutton, and Samuel W. Cope to Robert Paine - December 1, 1849, December 1, 1849, Robert Paine Papers, 1828-1882, Pitts Theology Library. https://digital.library.emory.edu/purl/767wm37r24-cor.